Determination of the uronic acid constituents of non-starch polysaccharides by high-performance liquid chromatography with pulsed amperometric detection

Abstract

A technique is described for measurement of the uronic acid constituents of non-starch polysaccharides (NSP) by high-performance liquid chromatography with pulsed amperometric detection using two sets of hydrolysis conditions. In one set of hydrolysis conditions the uronic acid-containing polymers are hydrolysed by prolonged treatment with sulfuric acid only; in the other, the hydrolysate obtained in the Englyst procedure for the measurement of dietary fibre as NSP is buffered to between pH 3.5 and 4 and the uronic acid-containing polymers present are depolymerized enzymically. The conditions for acid hydrolysis only or acid and enzymic hydrolysis of uronic acid-containing polymers optimized for a range of fruit, vegetable and cereal products. Values obtained for total uronic acids are very similar using either hydrolysis procedure, and are in good agreement with values obtained using the spectrophotometric assay as used in the Englyst procedure.